1. Field of the Invention
The present invention relates to a process and system for selecting mature sperm from a sperm population for assisted reproduction, and for intracytoplasmic sperm injection (ICSI) and determining mature sperm count and, in particular, to the use of a mature sperm binding substrate applied to a surface on which mature sperm, but no sperm with diminished maturity, selectively bind. The mature sperm binding substrate will also serve as laboratory testing material to determine whether some fertile or infertile men have a sperm maturation deficiency.
2. Description of Related Art
Assisted reproduction techniques in current use include intrauterine insemination of sperm, in vitro fertilization (IVF) of the egg with sperm, and ICSI and spermatid or other immature germ cell injection into oocytes. In the case of intrauterine insemination and conventional IVF, assisting the sperm selection process is not necessary, because the fertilization depends on a selection process that is based on physiological and specific interaction of sperm and oocyte. However, in severe male infertility requiring ICSI with ejaculated, epididymal or testicular sperm, the operator arbitrarily chooses and introduces the fertilizing male gamete regardless the maturity of the sperm.
In the ICSI process, the operator injects the sperm into the oocyte, thus overriding the steps of sperm-zona interaction which in conventional fertilization with mature sperm consists of the following steps: sperm-zona pellucida binding acrosome reaction of the spermatozoa, sperm penetration into the zona, fusion of the sperm and the oolemma, oocyte activation and creation of an embryo. Immature sperm do not bind to the zona because the development of the zona-binding site is part of the sperm maturation process. In the present ICSI procedure the operator may select both mature or immature spermatozoa. Immature spermatozoa, which have a higher incidence of faulty genetic material, and which prior to ICSI have never been part of the fertilization pool, will undoubtedly cause at least a portion of the pregnancies resulting from the ICSI process.
At the present time, the overt rate of congenital malformations and sex chromosome abnormalities in humans, although it is about double of the normally occurring rate, it is still very low in ICSI offspring. However, the oldest of these children are only a few years old, and thus it is not yet known if their individual development, growth, sexual maturation, fertility, cancer rate, life span and the rate of congenital malformation in their children are affected. An important goal would be to develop methods by which mature sperm, similar to those predominant in normal fertile men, whether arising from ejaculated semen, from the epididymis or testes, could be selected for ICSI. Such sperm selection process would maintain the risk of adverse fetal outcome at a level similar to that of couples reproducing by conventional methods based on sperm-oocyte interaction. Ideally, the selection technique would be able to select both motile and immotile mature sperm. A selection technique specific for mature sperm would also facilitate the determination of the proportion of mature sperm in husbands of infertile couples, in order to test male fertilization potential and determine the necessity and optimal choice among the available methods of assisted reproduction.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a method and system for distinguishing and selecting mature sperm from immature sperm.
It is another object of the present invention to provide a method and system for selecting mature sperm in which the motility indicates viability and is also able to select immotile but viable mature sperm. Non-viable sperm, because the integrity of the oocyte activator factor(s) and genetic material are diminished, are not desirable for ICSI.
A further object of the invention is to provide a method and system for selecting mature sperm which may be used in assisted reproduction techniques, particularly the ICSI method.
It is yet another object of the present invention to provide a testing method and system for determining mature sperm count in general sperm population men who are investigated for potential diminished fertility or infertility.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.